The present invention relates to methods and apparatus for erasing a recording on magnetic recording media for preparing the media for a new recording. An erasing means for such magnetic media has previously been described in Electronics, March 1, 1973, pages 73-76, and in U.S. Pat. No. 3,683,382. In both of the above references erasing means are disclosed wherein large electromagnets are used to prealign the reflecting elements in the recording medium. In both cases a combination of a constant and a varying electromagnetic field is used. It is stated that it is less efficient to use a permanent field only for prealigning the elements than the rotating vector field resulting from the combination of the varying and the permanent field. The varying magnetic field is created by connecting a solenoid to an AC source, and the constant field is created by connecting a corresponding solenoid to a DC source. The DC magnet may be replaced by a permanent magnet.
These known electromagnetic erasers are comparatively large and expensive, and the power consumption is too large for many potential applications.
According to the present invention there is provided both method and apparatus for erasing a record on a magnetic medium using a permanent magnetic field using one or more small magnets. One or more permanent magnets are used with a result that is not significantly inferior to erasing with a varying magnetic field created by the combination of an AC and DC electromagnet.
The present invention provides an erasing means which is both less expensive, smaller and which uses less power than the known erasing means.